On my computer, I have the manual power off switch in the front of the computer (that shuts off the computer or puts it into standby mode), and also the small toggle type switch on the back of the computer that shuts off the mobo.

There's really not much need to turn that PSU switch off at the back. The only time I ever use it is when I am moving my computer, or taking it apart. However, I do this before I actually unplug my computer.